The battle of Gettysburg, the bloodiest three days in U.S. war history, saw about 100,000 men fall. The entire Vietnam war involved about 55,000 U.S. casualties. A half-million dead and injured in one day is a staggering sum, almost more violence then we can conceive an army enduring.
Bible scholars have long contested the high numbers reported through the Chronicles, arguing that units of thousands may have been counted but with fewer actually present. With respect to the half-million figure, counting so many dead probably would have surpassed the capability of a field army anyhow, so we must rest with estimates and not be too insistent that the half-million number reflects a head count, man by man.
2 CHRONICLES 13:17 – 17 And Abijah and his people slew them with a great slaughter: so there fell down slain of Israel five hundred thousand chosen men.